1. Field of the Invention
The present invention relates to a process for preparing a heterocycle by catalytic reaction of an aromatic dinitrile and an amino alcohol.
2. Discussion of the Background
DE 2135644 describes a non-catalytic process for preparing cyclic imidic esters from aromatic nitriles and amino alkanols, wherein the process has a reaction time of more than 20 hours. The reaction is carried out under a protective gas in order to suppress by-product formation. The reaction mixture is worked up by methods including recrystallization.
DE 2153513 describes a process for preparing oxazines from N,N′-bis(3-halopropyl)dicarboxamides or bis(3-halopropyl)dicarboximidates in the presence of a base. The reaction mixture is worked up by recrystallization.
U.S. Pat. No. 4,806,267 describes a process for preparing a mixture of bisoxazines by reacting mixtures of amino alkanols with dinitriles in the presence of a cadmium nitrate catalyst or a zinc acetate catalyst, and xylene as a solvent. The reaction time is 10 or 20 hours.
Culbertson, B. M., Cyclic Imino Ethers in Step-Growth Polymerization, Progress of Polymer Science, 27, 579-626 (2002), describes the synthesis of oxazines by the reaction of nitriles and amino alcohols in the presence of a zinc acetate catalyst and xylene as a solvent.
EP 1548012 describes a catalytic process for preparing phenylenebisoxazolines by reaction of terephthalonitrile or isophthalonitrile with 1,2-amino alcohols in the presence of a zinc catalyst and xylene as a solvent. The reaction may be carried out in the absence of an additional solvent (e.g., xylene).